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https://issues.apache.org/jira/browse/CALCITE-4633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17357587#comment-17357587
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Julian Hyde commented on CALCITE-4633:
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Can you rewrite that query such that it reads fewer columns in the scan and
returns the same results? I don't think you can.
Possibly you could remove {{unit_sales}} (because it might be functionally
dependent on {{customer_id}} and {{store_id}} in that particular data set).
You could change {{count\(customer_id)}} to {{count\(*)}} and it will return
the same result - because customer_id is not null. (In fact {{RelBuilder}} will
do that rewrite for you.) But you'll still need to keep {{customer_id}} in the
{{union}}.
> Enable RelFieldTrimmer to trim fields on a distinct UNION
> ---------------------------------------------------------
>
> Key: CALCITE-4633
> URL: https://issues.apache.org/jira/browse/CALCITE-4633
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.26.0
> Reporter: Sean Broeder
> Assignee: Sean Broeder
> Priority: Major
> Fix For: 1.28.0
>
>
> Should be able to push a project to trim fields on top of distinct union
> without changing results.
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